Feature: use independent auto-completion file for each app in pwsh

[dysuby]

Instead of writing the auto-completion script into user profile script, this PR write the content into a single file and source it in profile script. So that we can have a clean profile file.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (c3a4c72) to head (888f196). Report is 230 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #267   +/-   ##
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  Coverage   100.00%   100.00%           
=========================================
  Files          242       242           
  Lines         4508      4520   +12     
=========================================
+ Hits          4508      4520   +12     

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